This invention relates to the application of industrial slags to manufacture ceramic microspheres for use in cementing applications, more particularly, to the manufacturing of controlled size hollow, cellular and solid microspheres, which have latent pozzolanic properties as well as weak magnetic properties, from blast furnace slags and industrial steel furnace slags. The ceramic microspheres can be used for conventional cementing oil and gas well operations, for instance to replace Portland Cement in mud-to-cement (MTC) technology and/or blast furnace slag and also for the construction areas.
Portland cement is a hydraulic cement made by heating a limestone and clay mixture in a kiln and pulverizing the resulting material. The most common use for Portland cement is in the production of concrete. Portland cement is also used in mortars, such as with sand and water only, for plasters and screeds, and in grouts, such as cement/water mixes squeezed into gaps to consolidate foundations, road-beds, etc.
Blast furnace slag (BFS) is a by-product produced in the manufacturing of iron, iron ore, iron scrap and limestone fluxes or dolomite fluxes. BFS is nonmetallic and consists primarily of silicates, alumninosilicates and calcium-alumina-silicates.
Industrial steel furnace slags (SFS) are a by-product in the manufacturing of steel and/or steel alloys. SFS is a nonmetallic product that is developed simultaneously with steel in basic oxygen, electric, or open-hearth furnaces. It consists of calcium silicates and ferrites combined with fused and mineralogically combined oxides of iron, aluminum, manganese, calcium and magnesium.
In cementing applications, such as steam injection techniques and other oil extraction processes that require increased well temperatures, the cementing material used must be able to withstand elevated temperature and thermal cycling associated with steam flood. The conventional Portland cement and also water based drilling fluids mixed with Portland cement exhibit high thermal degradations. This degradation damages the well resulting in repairs which increase operation costs. In steam injection techniques, the use of ceramic microspheres in cementing applications leads to a lightweight grout that is resistant to elevated temperatures and thermal cycling.
In some regions of the world where steam injection techniques are employed, BFS is not readily available and is therefore imported. The high costs associated with importing BFS compounded by the unknown heterogeneous chemical composition of the BFS, unknown remaining crystalline phases in the BFS and the potential need for an additional milling process is a disadvantage suffered by regions of the world that do not produce BFS. By combining hollow microspheres of composition similar to BFS, steam injection resilient lightweight grouts of low density have been obtained.
The use of ceramic microspheres for cementing applications results in substantial savings by reducing the environmental impact of the cementing application, reducing the consumption of oilfield cement and by replacing the need to import expensive cementing additives.
The ceramic microspheres for cementing applications of the present invention may replace BFS and/or Portland Cement in any well cementing operation. The ceramic microspheres of the present invention are an advantageous well cementing constituent that may be successfully implemented in differing temperature dependent processes, such as the steam injection technique employed for heavy crude oil extraction.